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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

FXUS66 KSGX 211612

Area Forecast Discussion
National Weather Service San Diego CA
900 AM PDT Thu Jun 21 2018

High pressure aloft will bring hot weather to the deserts today 
through Friday, but onshore flow and a strong marine layer will 
continue the mild weather along the coast with extensive night and 
morning low clouds, and only partial afternoon clearing. The high 
pressure system will weaken over the weekend and bring cooler 
weather to inland areas. Fair weather will continue early next week 
with temperatures increasing slightly, but night and morning low 
clouds will continue near the coast.



Stratus was widespread in most areas west of the mountains early 
this morning, including quite a few parts of the Inland Empire. 
There was even a little bit of drizzle around San Diego Int'l 
Airport and North Island. NKX sounding this morning had the marine 
inversion base at 1300 ft MSL but with an inversion strength of 14 
deg C. This will combine with the weak eddy to result in very slow 
clearing along the coast, with many beaches likely staying cloudy 
this afternoon. Inland areas were already starting to clear, and 
sunny skies will prevail by 10-11 AM everywhere east of about 5 
miles from the coast. Of course, the deserts will be hot today, 
though slightly hotter Friday.

High pressure aloft is centered over NW Sonora, and a roughly east-
west ridge of high pressure will continue today and then shift a 
little bit south farther into Mexico Friday and Saturday as 
troughing developing to the north. While heights fall slightly 
Friday, 850 MB temps peak then, so most of the deserts, especially 
the lower deserts, will have their hottest day Friday. The lower 
deserts should be mostly around 110 or slightly higher today and 112-
115 Friday. The high deserts will be 102-108. An upper low moving 
through Idaho/northern Nevada/northern Utah Saturday will bring weak 
cyclonic flow aloft here, versus the previous anti-cyclonic flow and 
also force the high to be farther south and also farther west over 
the ocean. It will end up being 5-8 deg F cooler over inland areas 
Saturday, with little change Sunday. While clouds will likely linger 
along the coast today/Friday, the cooling aloft should result in 
better afternoon clearing over the weekend. Some warming could 
return early next week as the high aloft gradually expands, 
extending all the way from the Central Pacific to Texas. Monsoonal 
moisture should stay well to the southeast, so no precipitation is 
expected through late next week except for very minor drizzle from 
the marine layer at times.


211545Z...Coast/Valleys...Marine layer a little deeper and cloud 
layer a little thicker this morning with OVC008-012 Tops 2200 ft MSL 
extending all the way to KONT and KRAL early this morning where vis 
was 3-5 miles in FG/HZ. The low clouds will clear from inland areas 
by late morning, but will likely linger along the immediate coast 
throughout the day. Clearing at the coastal airports (KSAN, KCRQ, 
KSNA) will be limited to between 21-24Z. 

Tonight: Low stratus with BKN-OVC008-012 Tops 2000 ft spreading back 
inland into the valleys again through 14Z Friday. 

Mountains/Deserts...Mostly clear with unrestricted VIS through 
Friday morning. 


No hazardous marine weather is expected through Monday.


Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


CA...Excessive Heat Warning from 11 AM this morning to 8 PM PDT 
     Friday for Apple and Lucerne Valleys-Coachella Valley-San 
     Diego County Deserts-San Gorgonio Pass Near Banning.